Mixing 4Gb and 8Gb memory on BL460c

[John Dunne]

Hi,
are there any performance implications with mixing a HP 8GB FBD PC2-5300 2x4GB Kit and a HP 4GB FBD PC2-5300 2x2GB Kit on a HP BL460c.

I have been told on normal proliant servers there can be a performance hit due to interleaving.

We have 2 16Gb (4x4Gb) HP ProLiant BL460c 2 x Xeon Quad Core (E5440) 2.83 GHz for a virtualisation project and are buying 6 more with 32Gb (4x8Gb).

I am proposing we distribute the memory to all servers to give 8 servers with 28Gb (3x8Gb + 1x4Gb) and was interested to find out if there are any disadvantages to doing this.

Thanks

[Blazhev_1]

Hi,

even on G5 proliant servers this configuration will not be supported and the server will not boot at all.

If you mix 4GB and 8Gb DIMMs in the same server there is no problem. Problem is that the DIMMs must be installed in pairs, exactly because of interleaving.

This means that you should have even number of identical modules.

Check the memory population rules for BL460c :

http://h18004.www1.hp.com/products/quickspecs/12518_div/12518_div.html#Memory

you will break rule 4.

You can install minimum 2x4GB in one server (slot 1&3), the rest can be 8GB.

[Adrian Clint]

Blazhev

He's not going to break any rules. He's talking about mixing kits not single DIMMs.
He has 8x 4GB kits & 24x 8GB kits.

I think the performance issues will depend on how the OS lays out the memory.

[TarunJain]

Dear John,

This is a supported configuration & should not cause any performance setback.
These servers Supports 2x1 memory interleaving.

Don't worry & install pairs of memory modules.

Interleaving claims to improves the performance & it can't be disabled in these servers.

Regards,
Tarun

[Blazhev_1]

well now I see his first sentence, that he is talking really about kits.
So config seems really ok, sorry, my mistake